If you're big into iOS, AirPlay is a great method for streaming audio and video content between your Apple devices. But it's not perfect. Your iPhone and iPad can only stream out, for example — not the other way around. And your AppleTV will only accept the file formats supported in iTunes. These aren't quite deal breakers, but they can be annoying restrictions.

Luckily, there are are a few third-party solutions with AirPlay support — and they enable your Apple devices to do all the things they normally can't. If you've ever wondered how to re-direct audio (and sometimes video) from nearly any application or player to your iOS device — including all that new Spotify goodness — here's how.

First up is a piece of software called AirFoil ($25, though a free trial is available) . Whereas iTunes is limited to content in your music or video library, AirFoil can stream audio from any Mac or Windows application, essentially turning your AppleTV into a fancy set of wireless speaker. This is done by "hijacking" an application before launch, though you can also divert your system's entire audio output if you so choose. If you're a fan of NPR's live concert archive, you can hijack Chrome and send those recordings to your AppleTV. Or perhaps you'd like to send your Team Fortress 2 audio to the HDTV's sound system. That's totally possible too (albeit, with an ever-so-slight sense of lag).

We also mentioned the ability to send AirPlay audio to iPhones and iPads. This isn't usually possible, but a companion app called AirFoil Speakers can turn your iOS device into an AirPlay receiver. This can be useful for mobile listening on your local network, and some applications — such as rdio and Spotify — even allow you to control the audio stream remotely from your iOS device.

AirFoil isn't perfect, however. The software can't stream system audio under OS X Lion (yet), which means you'll need to hijack audio on a per-application basis. Also, it's important to note that AirFoil does not handle streaming video. The best you can do is stream your Hulu or Netflix audio to an external receiver, while the video plays on your laptop or desktop screen. This too comes with caveats, however, as you'll need to use the built-in AirFoil Video Player — essentially a glorified web-browser — to play your web video content without audio lag (OS X only).

However, there is another solution called AirFlick — which does support video, and has the added bonus of being free. We wouldn't quite call this an alternative to AirFoil, as it sticks to streaming more traditional content and file formats, instead of system audio. However, it does give you the ability to stream content to your AppleTV — and even other Macs, using its sister app, AirPlayer.

AirFlick is ad-supported — but unlike AirFoil, it's free. Can you really complain?

Out of the box, AirFlick isn't all that useful. It essentially acts as a third-party iTunes, and only streams content natively supported by the AppleTV. However, when used in conjunction with another utility, called AirVideo Client, AirFlick can stream transcoded audio and video files from your collection in a format the AppleTV understands. Think of it as a PS3MediaCenter-style app for iOS devices, though with a few extra steps to set up.

Have your own weird and wonderful approach for streaming audio and video content to an iOS device or AppleTV? Let us know!